The invention relates to an integrated circuit and to a method of monitoring physical operating parameters of such an integrated circuit.
US Patent Application No. 2004/0128115 describes an integrated circuit with sensors for measuring the value of power supply noise. A shift register is provided to read out data from the sensors. Sensors are provided for determining a maximum power supply noise voltage and a minimum power supply noise voltage. During operation each sensor sweeps a reference voltage through a range of values until the reference voltage is found to exceed the maximum or minimum power supply noise voltage. The sensor captures digital values that represent the maximum and minimum power supply noise voltages and loads the captured digital values into the shift register. These digital values are then serially shifted out of the integrated circuit using the shift register.
PCT Patent application No 2004/068156 similarly describes capture of digital data that represents a measured physical operating parameter into a scan chain, although no voltage sweep to determine maximum and minimum voltages is mentioned. European Patent application No. 647905 describes a test circuit that performs a test by comparing voltages with reference voltage and shifts out the comparison results through a scan chain.
With the continual increase in circuit complexity there is a need to increase the number of sensing circuits for sensing physical parameters in an integrated circuit. It is desirable to measure physical operating parameters such as temperature and power supply noise, cross-talk clock jitter at many different places in an integrated circuit, in order to monitor whether the integrated circuit functions properly. However, for the function performed by the integrated the sensing circuits for these physical operating parameters are valueless overhead. Therefore it is desirable to minimize the circuit area occupied by the sensing circuits.